Presently the market has a limited number of marginally effective or economical ways to address the problem of delaminating unintentionally voided masonry piers and/or walls usually associated with separation between leaves (leafs or layers) of masonry. A restorer has the choice of dismantling and reconstructing the affected masonry at great expense and occasional danger, or using an array of existing, externally applied products and systems to try to knit the masonry back together but never fully restoring its structural integrity. Some of the prior options which attempt to but do not meet current needs or accomplish all of the functions of tying and cementing voided masonry back together are as follow:
a) Injection Grouting Systems into Voids: These systems require numerous drill holes to inject grout (to attempt to “glue” the masonry together) and sometimes separate drill holes to install anchors, if needed for additional tying of the masonry. Such systems can only partially rely on the adhesiveness of the grout to hold the masonry together, and must therefore rely on the presence of ties, and have little or no mechanism for scoping and cleaning the voids that must be filled, thereby establishing a proper, cementing bond. Thus, these systems can lead to major problems in the stabilization of masonry and require numerous drill holes which can increase the potential danger of the repair operation. Some grout injection systems do not rely on ties, however, these employ high strength resin or cement based grout formulations that are not physically compatible with the parent masonry. Also, these systems cannot be used at below 32 degrees F. temperature as the grout will not cure properly and could freeze.
b) Epoxy-Based (Adhesive) Anchor Systems: These systems involve the insertion of tubular screens into holes that are drilled through the voided masonry, partial filling of the screens with epoxy, and then insertion of metal rods. These provide limited reliability and are not effective in spanning over large voids as not enough containment pressure is developed within the screen to uniformly cover all contact surfaces before the adhesive oozes out of the screen. Also, these systems do not attempt to actually fill the voids (in order to cement the leaves back together), and therefore have very limited shear capacity across wider voids. These systems are not generally suitable for cold temperature installations where the curing of the adhesive is slowed or halted.
c) Mechanical Wedge (Mechanical) Anchor Based Systems: These systems transfer no shear loads and make not attempt to fill the voids between leaves of masonry, rather, they simply keep the voids from widening or narrowing.
d) Dry-Set Helical (Mechanical) Anchor Systems: These systems make no attempt to fill the voids and must be vibrated and driven into place, potentially damaging and loosening delicate masonry wall systems during use.
e) Grouted Sock (Adhesion)Anchor Systems: These systems have only a moderate amount of shear capacity and contain the grout so that it does not flow into the voids. These systems will also not work in temperatures of below 32 degrees F. as the grout will not cure.